Reduction furnace



`April 18, 1933. 1 D, MORGAN Y 1,904,508

' REDUCTION FURNACE Filed April 17, 1931 2 Sheets-Sheet l Svwmtoi JOHND. MORGAN 32,121, his @Home/:g-

I April 18, 1933. D. MORGAN 1 1,904,508

REDUCTION FURNAGE f Filed April 17, 1,931 2 Sheets-Sheet 2 f Svwento'c yJOHN D. MORGAN 3513 has 61u M3 M7@ Patented Apr. 18, 1933 UNITED STATESPATENT ori-'ice JOHN E. MORGAN, 0F SOTH ORANGE, NEW JERSEY, ASSIGNOR TODOHE'BTY I COMPANY, 0F NEW YORK, N. Y., A CORPORATION 0l' DELAWAREREDUCTION '.FJ'BNACE Application led April 17, 1931. Serial No. 580,796.

This invention relates to furnaces for production of phosphorus and forsimilar purposes, and more particularly to an improved reduction furnaceadapted to reduce a charge in such a manner as to allow a continuousoperation of the apparatus. This application is a continuation in partof pending application Serial No. 312,574 filed October 15th, 1928. 1

The existing forms of apparatus which may be operated to reduce naturalrock phoshates and for similar purposes give at best ut a faulty andineiiicient operation in that they merely superfcially preheat thecharge to only a comparatively low temperature thus placing the burdenof reduction in one limited portion of the ap aratus. In addition suchexistin forms o ap aratus do not operate to re. eat the comp ete chargeto partially re uce the same but merely to regenerate a portion of theheat of the gases leaving the a paratus.

Accor ingly one of the objects of the present invention is to provide aform ofappa ratus for the continuous reduction of natural rockphosphates and for similar purposes which is slmple in construction andeflicient in operation.

Another object. of the present invention is to provide a form vofapparatus which will operate to reduce the charge in the preheatin zoneas well as in the final reduction zone anfl in so doing 4distribute theburden of re# duction throughout the a paratus.

Still another object o the present invention is to provide a form of aparatus which will operate to heat the comp ete charge in the preheatingzone to a reduction temperature and in so doing reduce the amount ofenergy necessary to be applied in the final reduction zone.

A further defect in the existing forms of reduction apparatus lies inthe fact that no thought is given to the means of feeding the charge,which char is generally fed into the apparatus in a eranged andhaphazard state, thus tending to ineiiiciency in the preheating zone. Y*v Accordingly another object of the resent 'the combustion the charge insuch an orderly state and arrangement that the eiiiciency of thepreheating zone will be greatly enhanced,k

Other objects and advantages of the present invention will be apparentfrom the following detailed description taken in connection with' theaccompanying drawings in which: y

Fig. 1 is a. longitudinal vertical section throu h a furnace constructedin accordance with t e present invention;

Fig. 2 is a vertical section of an electric melting pot whichconstitutes a part of the apparatus according to the present invention;

Fig. 3 is a section of the furnace taken on line 3-3 of Fig. 1;

` Fig. 4 is a perspective view of a briquette which is'used in chargingthe furnace;

Fig. 5 is a vertical sectional view of a modiication of the furnaceaccording to the present invention;

Fig. 6 is an end view of the furnace shown in Fig. 5 looking from theleft of this figure, parts being broken away;

Fig. 7 is a section of the furnace taken on line 7-7 ofiFig. 5.

In the drawmgs; 2 indicates a furnace according to the present inventionand which may be operated for the simultaneous production o phosphorusand cement and for similar pur `oses. The furnace 2 comprises anelongate heating hearth or mule 4 which is inclined at an angle lessthan the angle of slip of the charge which is to be fed therethrough.The heating hearth 4 is constructed so as to form therein a passage 6through which the charge in the form of briquettes 8 is fed and alcombustion chamber 10 for the t combustion of gases produced within theapparatus. The walls 12 of the passage 6 and chamber 1G are composed ofa dark colored high heat conducting refractory material and are backedup by a layer or series of layers 14 of a light colored heatinsulatingmaterial. The surfaces vof the passage 6 of the combustion chamber' 10are treated with a chromium-compound in order to present to the gasesproduced within the- 53 invention is to provide means for eedingapparatus a surface which will not corrode of these. electrical heatingelements, and they may be operated in any manner so as to obtain theheat required under the existing conditions. Also within the hearth 4and immediately above-the combustion chamber 10 are located fuel burners18 which may be operated to give a similar result as the electricalheating elements either by themselves or in conjunction therewith. Atthe inlet end of the hearth 4 is a pusher mechanism 20 which l may beofany well-known type constructed so as to prevent the escape of` gasesas the charge is fed into the hearth. At the charge inlet end of thehearth 4 is also a conduit 22 leading 'from the combustion chamber 10and which acts as an outlet for the gases of combustion.

At the discharge end of the hearth 4 is an electric furnace or meltingpot 24 comprising a meltin chamber 26 with walls 28 of a dark color highheat-conducting refractory material, the surfaces of which are treats edwith a chromium compound `such as chromic acid. The material surroundingthe walls 28 is composed of a layer or layers 30 of a light coloredheat-insulating refractory. Electrodes 32 extend into the meltingchamber 26 and form with the material undergoing 4 treatment in thechamber 26 an electric circuit by means of which the material i: heatedand maintained in a liquid state. At the bottom of the chamber 26 aretaps 34 and 36, tap 34 being located at a lower level than tap 36,

the purpose of which will be hereinafter exing to the present invention,t

5 pushed through the passage 6 slowly and is plained. At the top of thechamber 26 is an air inlet pipe 218 t rough which air, which has beenpreheated in a eat interchanger 40 by means of heat interchange with thehot products of combination being lead out through conduit 22, isintroduced into the chamber 26 for thel purpose of burning with thegases'produced within the apparatus.

In the operation of the apparatus accorde charge in the form ofbriquettes 8 is fed into the charge inlet end of the hearth 4 and ispushed through the passage 6 in a uniform ribbon by means of the pushermechanism 20. The charge is subjected to a heating action by means ofthe heating elements 16 or the fuell burners 18 or if a highertemperature is required, a combination of both the heating elements 16and the. burners 18.' After passing through the passa 6 the charge fallsinto the melti'ng cham r 26 and is raised to a still higher temperature'b means of the electric current passing t rough the electrodes 32 andthrough the charge itself. In the meltin chamber 26 the charge isreduced to a liquid and'is tap d oi at intervals through the tap 36, asuiiicient amount of liquid material however bein always maintainedwithin the meltin c amber to cover the ends of the electro es and tocomplete the electric circuit between the electrodes. This is of greatimgortance in that if the liquid material were rained from the chamber26 leaving only an, imperfect contact of solid material between theelectrodes there would-be a greater period of time required and agreater amount of current necessary to reduce the `solid content of thechamber to a liquid state. The metallic substances and impurities whichmay be present in' the charge settle to the bottom of theliquid withinthe chamber 26 and may be drained off through the tap 34. If theapparatus is operated for the production of substances such as cement,themetallic materials must be drained off in order to prevent them fromcompleting the circuit between the electrodes with a subsequent loweringof resistance and loss of heat.

As the gases which are produced by the heating rocess both in thepassage 6 and the cham r 26 rise to the roof of the melting chamber theyare met by a stream of aix which has -been preheated. in heatinterchanger 40 and which flows into the chamber 26 through pipe 38. Bythis means the arf burned and the gaseous products an tht flames ofcombustion pass up through the combustion chamber 10 im arting theirheat of combustion throu h wa 1'12 to passage t through which'the c argeis being fed, thu: acting to preheat the same. Once the proces isoperating eiciently, and the charge is sucl as to generate combustiblegases, it is possibh to' run without any heating aid from eithei theelectric heating elements 16 or fuel burn ers 18 and to heat the chargein .the passag 6 merely by the heat absorbed from the com bustion of thegases in the combustion cham *ber 10. Such combustion will radiate suicient heat to raise the charge in passage 6 t the usual necessarytemperature.

The gaseous products of combustion wil flow from the combustion chamberil through the outlet pipe 22 into heat inter changer 40 whereintheyimpart a portion o Within the hearth 44 is a passage 46 throughwhich the charge in the form of briquettes 48 are fed and a chamber 50in which the charge is finally heated and in which the greater portionof the gases are driven olf rom the charge.

Above the passage 46 is a combustion chamber 52 which is provided withan inlet 54 for the gases driven off from the charge, an air inlet 56and an outlet 58 for the gaseous products of combustion. Air for thecombustion of the gases evolving from the charge is injected into theapparatus through a pi 60 into a heat interchanger 62 where it a orbsart of the heat of the gaseous products o combustion such gaseousproducts leaving the combustion chamber through the outlet 58 and pipe64, and through a pipe 66 into the'combustlon chamber 52 by Way of theinlet 56.

The Walls 68 of the passage .46 of the combustion chamber 52 and alsothe walls of the chamber 50 are composed of a dalr colored highheat-conducting refractory material and are backed up by a layer orseries of layers 70 o-a light colored heat-insulating material. Thesurfaces of the passage 46, the combustion chamber 52 and the chamberare treated with a chromium compound such as chromic acid in order toprevent sticking of the charge and in order to provide an antl-corrosivesurface under. the conditions existing in such an apparatus.

Below the chamber 50 are placed electric heating elements 72 for thepurpose of raising the charge to the necessary temperature for reaction.elements is not limited and the may extend for the full length of theheartn, heating the charge in passage 46 as well as in the chamber 50.Fuel burners 74 are' also provided for heating the charge and may beused by themselves or in comunction with the electric heating elements.When the charge is such as to generate combustible gases and thecombustion of the produced gases is occurrin in chamber 52, it has beenfound that no ad itional means for heating the assage 46 is required,since the heat of combustion of such gases by itself is suicient toraise the charge to the necessary temperature before This mechanismmayebe of any it enters chamber 50.

At the inlet end of the passage 46 is pro-- vided a mechanism 76 forfeedingxthe charge. own form, the onle provision ing however that thecharge fed in such a way that there be no escape of gases during theperiod of injection.

At the outlet end of the heating hearth are grinders 78 arranged toreceive -the briquettes 48 as they pass out of the chamber 50. As anintegral art of the hearth 44 and at the outlet en thereof is a chamber80 which also encloses the grinders 78.- At

The number of such heating the bottom of the chamber is a vate mechanism84 which acts as a closure between the chamber 8O and a discharge chute82. Leading into the chamber 80 and directed toward the grinders 78 aregas inlet ipes 86, the urpose of -Which will hereina ter be descri d.

The chamber 80 also contains an outlet 88 which connects with a chamber90. The chamber extends directlybeneath and for the full length of thechamber 50 and-has a roof 92 in which the bricks are laid rather looselyallowing crevices between the bricks for the escape of gases from thechamber 90 which roof also acts as a base on which the charge slides asit passes through the hearth.

The function of the outlet 88 and the chamber 4 90 will be hereinaftermore fully described.

In the operation of this modification of the invention, the charge inthe form of bri quettes 48 is fed through the charging mechanism 76 intothe passage 46 through which, as well as through chamber 50 it slides bygravity. If necessary, the charge is heated by means of fuel burners 74or electric heating elements 72. If however the apparatus has been inoperation for a period and gases are beinv driven olf from the charge,it will be founda that the heat of combustion of such gases, whichcombustion occurs in chamber 52 by means of preheated air entering thechamber through inlet 56, will serve to preheat the charge to asuiiicient temperature so as to obviate an'l additional method ofheating the charge while it is passing through passage 46.

As the charge slides through chamber 50 in a uniform relatively thin andwide ribbon, it is heated by electric heating elements 72 and is raisedto a suicient temperature to drive oi all the gaseous constituents.These gaseous products flow back through chamber 50 throu h inlet 54,are burned in the combustion c amber 52 by means of air flowing into thechamber through inlet 56 and leave the chamber 52 through outlet 58. Theburning gases How through the heat interchanger 62 where they preheatthe incoming air and are ledoi through pipe 64 to storage, or furtherprocessing.

The spent portion of the charge on reaching the outlet end of the hearthis ground by means of grinders 78 and falls into chamber 80. As the massof ground material in chamber 80 increases, itis intermittently droppedinto chamber 82h means of the ate mechanism 84 from w ence it is discarged di- ,45 not va temperature is fipplied. It has been found howeverthat su cient operation may be had without application of a highertemperature if a stream of inert as is allowed tocome into contact withthe c arge undergoing treatment. Therefore, in order to maintain aneicient operation of the apparatus at a practically constant temperatureby avoiding the formation of a coating on the charge,'and in order toallow the reaction of the charge to o to completion, a stream of aninert gas suc as nitrogen is introduced into the apparatus throughtheinlet pipe 86. This as circulates around thechamber 80 absorb part,of the sensible heat of the spent materia which has fallen into thechamber, iows .over grinders. 7 8, thus partially cooling them, and thenHows mto chamber 90 by way of outlet 88, and also into chamber 50 b wayof the charge outlet opening. The ot gases in chamber 90 pass throughthe roof 92 b way. Aof the crevices therein and mix with t e gas inchamber 50. In this waythe neutral while intimately contacting with thebriquetted charge sliding through chamber 50, im arts a portion of itsheat to the 'charge and then in mixture with the produced com sitionaccordin to the desired, product ut it has been ound that in'order toobtain the maximum eiiiciency of the apparatus, the physical shape ofthel charge should A briquetted charge in the form shown 1n Fig. 4 ofthe drawings has been found to be of highly practical advantage inoperating the apparatus. Such form of charge of relatively very thincross section 5 and with lateral and longitudinal scoring on both sidesthereof will present a lar heating surface and, no part of thebriquetted char being far from the surface, 1t will continuouslyberaised to substantially the same temperature throughout thus givinggreater eiiciency in the heating operation; In both forms of theapparatus according to the resent invention, the char e in the formobriquettes 'such as shown 1n Fig. 4 is f ed in a uniform relativelythin and wide ribbon. It has been found that the high heatingkeiciencynecessa in such apparatus is lac ing if the charge 1s fed into thefurnace in a thick layer or in a haphazard manner. In using the form ofcharge as shown in gas heating said charge gasesa. passes through theinlet 54 and the chamber The charge will obviously differ greatly inFig. 4 and as above described, andin feeding such charge into theapparatus 1n a uniform ribbon the apparatus will operate at its highestefficiency and the constituents desired will be recovered from thechargewith the least possible expenditure of heat ener Havin thus describedthe inventiomw at is claime as new is l 1. A furnace comprising incombination a stationary sloping heating hearth, electrical resistanceheating units for heating'a charge being fed through said hearth, meansfor feeding a charge through said hearth in a uniform, relatively thinand wide ribbon, means for breaking said charge as it leaves saidhearth, means at the inlet of said feeding means adapted to allow thefeeding of said charge without allowing the escape of gases, meansdirectly connected to the discharge end of said hearth for receivingspent material therefrom, means for regenerating the heat of said spentmaterial, means for erated, and means for heating said charge by tieheat of combustion of the gases develope 2. A furnace comprising incombination a stationary sloping heating hearth, means for applying heatto said hearth, means forfeeding through said hearth a preheated char eby the heat thus regen in' a uniformrelativelythin and wide ri bon,means at the inlet of said feeding means adapted to allow the feeding ofsaid charge without allowing the escape of gases, and means directlyconnected to the discharge end of said hearth for receiving spentmaterial therefrom.

In testimony whereof I afiix my s' nature.

JOHN D. MOR AN.

